The invention relates generally to multiple friction plate clutches for motor vehicle drive line components and more specifically to friction plate clutches having an internal reaction force circuit for use in pairs with a front or rear axle.
Vehicle drive line and control systems having both electric and hydraulic modulating clutches have found broad application in adaptive vehicle drive systems. Such systems generally monitor the speeds of the front and rear drive shaft or compute such speeds by averaging individual readings of the two front and two rear wheels and, upon determining a speed difference between the drive shaft speeds or average speeds of the wheels, energize the modulating clutch according to a predetermined program to drive the speed difference and thus wheel slip toward zero. Such systems may also monitor and adjust modulating clutch activity in response to throttle position, steering angle and other variables.
Typically, such modulating clutches are physically disposed in a transfer case, adjacent and driven by the output of the vehicle transmission, and operably disposed between the primary and secondary drive lines. Such systems are disposed in co-owned U.S. Pat. No. 5,407,024 granted Apr. 18, 1995 and U.S. Pat. No. 5,485,894 granted Jan. 23, 1996.
An alternate approach to vehicle skid control comprehends association of an individually operable clutch with each axle of a secondary, that is, part-time drive line. Selective, modulating activation of one or both of the clutches directs drive torque to one or both secondary drive wheels to adjust or correct vehicle yaw. An early system utilizing hydraulic clutches is disclosed in U.S. Pat. No. 4,681,180. Here, a control unit having steering angle, vehicle speed and engine torque inputs and adjust torque distribution between only the two rear wheels.
U.S. Pat. Nos. 5,195,901 and 5,119,900 both teach a vehicle having two independently operable rear axle clutches in a drive line which provides primary drive torque to the front wheels and selectively and independently provides torque to the rear wheels.
In U.S. Pat. No. 5,353,889, a rear axle includes a pair of hydraulically operated independent clutches controlled by associated hydraulic pressure clutches and pumps.
In U.S. Pat. No. 5,383,378, a twin clutch axle disposed at the front of a vehicle provide drive torque to the front (secondary) drive wheel in response to steering angle. U.S. Pat. No. 5,540,119 teaches a differential drive assembly for transferring rotational power without the use of conventional differential gearing. The device utilizes pairs of clutches and cam mechanisms which actuate said clutches in response a predetermined relative rotation.
While many problems have been addressed and new operational schemes achieved by the devices found in the prior art, it is apparent that certain problems have not been addressed. For example, it should be appreciated that, according to Newton""s third law of motion, the direct or action force generated by a clutch operator to compress an adjacent clutch pack creates an equal and opposite reaction force which is transmitted through whatever structural components of the clutch assembly constitute the reaction force path or circuit.
Typically, such reaction force path will be through or contained in an outer housing in devices where the clutch pack is disposed adjacent the clutch operator and both are contained within the housing. Such a configuration can apply significant reaction force, not only to the housing, but also to whatever fasteners are utilized to secure the housing components together. Such a configuration can be disadvantageous, causing either fastener or housing failure or necessitating heavy and therefore costly housing and fastener configurations. Accurately controlled modulation of the clutches may also be compromised due to flexure or distortion of the housing or other components in the reaction force path. Accordingly, the operation of devices containing such clutches may be compromised. The present invention addresses such matters.
A clutch assembly for disposition in a motor vehicle drive line includes an internal reaction force circuit. The clutch assembly includes a multiple plate or disc friction clutch disposed adjacent an operator assembly which selectively applies compressive force to the friction clutch to selectively transfer torque therethrough. The clutch components are disposed on an elongate member. The elongate member includes a preferably integrally formed circular plate or flange which functions as a first stop against which one side of the clutch pack abuts. A circular collar which may, in fact, be an anti-friction bearing is retained on the elongate member by a pair of snap rings. The circular collar or anti-friction bearing functions as a second stop against which one side of the operator assembly abuts. The elongate member thus functions as a reaction force member and self-contains the reaction force generated by the clutch operation. The clutch operator may be a ball ramp assembly which is actuated by an electromagnetic coil. Alternatively, the operator may include an electric motor and cam assembly which generates compressive force. Direct acting hydraulic or air driven piston and cylinder operators or pilot and main clutches which are electrically, pneumatically or hydraulically operated are also useful with and within the scope of the present invention.
The clutch finds application in motor vehicle drive line components such as a rear (secondary) axles in which it is disposed in pairs to independently control torque supplied to each axle and in other applications where it is advantageous to contain or ground the reaction force generated by and associated with the clutch operator within the clutch structure rather than its housing.
It is thus an object of the present invention to provide a multiple friction plate clutch having an internal reaction force path.
It is a still further object of the present invention to provide a multiple friction plate clutch and operator which are juxtaposed upon an elongate member which functions as the reaction force return path.
It is a still further object of the present invention to provide a multiple plate friction clutch assembly having an internal reaction force path for use in motor vehicle drive lines.
It is a still further object of the present invention to provide a multiple plate friction clutch assembly having an internal reaction force circuit for use in pairs in a rear (secondary) axle independently controlling torque delivery to associated wheels.
It is a still further object of the present invention to provide a multiple friction plate clutch and operator assembly are juxtaposed and assembled upon a common member which functions as a reaction force containing member.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like numbers refer to the same component, element or feature.